A call between communication terminals that occurs using wireless LAN system have a plurality of access points provided, and is realized by wirelessly transferring voice packets between communication terminals and access points that are connected to the LAN.
Normally, with this kind of access points, since the communication capacity that can be allocated for wireless communication is limited, sometimes it is not possible to satisfy the relaying requests of all of the calls. In such a case, it is necessary to limit the relaying requests of calls. For example, a control method of receiving calls is disclosed in Japanese Laid-open Patent Publication No. 2006-339969, in which, if calls through at least two or more telephone lines reach approximately at the same time, one of the telephone lines is selected on the side of the IP phone (communication terminal) based on a priority order that is set in advance.
With the control method that is disclosed in Japanese Laid-open Patent Publication No. 2006-339969, regardless of the state of the communication lines provided for a communication terminal, the priority of a new call for the communication terminal is determined by the communication terminal itself. However, under a state in which communication lines are congested, this new call does not reach the receiving terminal, and it is not possible for the receiving terminal to receive the call even if the priority of the new call is high. Also, under the state in which the communication lines are congested, it is not possible for the communication terminal to establish a call that is high in priority.